Natural History of Secundum ASD in Preterm and Term Neonates: A Comparative Study.

Atrial septal defects (ASDs) are common in neonates. Although past studies suggest ASDs  ≥ 3 mm in term neonates (TNs) are less likely to close, there is paucity of data regarding the natural history in preterm neonates (PNs), information that would inform surveillance. We sought to compare spontaneous closure rates and need for intervention for ASDs in TNs/near term (≥ 36 weeks) versus PNs (< 36 weeks). We included all TNs and PNs who underwent echocardiography at ≤ 1 month between 2010 and 2018 in our institution with an ASD ≥ 3 mm, without major congenital heart disease, and with repeat echocardiogram(s). Spontaneous resolution was defined as size diminution to < 3 mm or closure. We included 156 TNs (mean gestational age at birth 38.6 ± 1.4 weeks) and 156 PNs (29.6 ± 3.7 weeks) with a mean age at follow-up of 16 ± 19 and 15 ± 21 months, respectively (p = 0.76). Based on maximum color Doppler diameter, in TNs, ASD resolution occurred in 95% of small (3-5 mm), 87% of moderate (5.1-8 mm), and 60% of large (> 8 mm) defects; whereas, in PNs, resolution occurred in 79% of small, 76% of moderate, and 33% of large ASDs. There was a significant association between size and ASD resolution in TNs (p = 0.003), but not PNs (p = 0.17). Overall, ASD resolution rate was higher in TNs (89%) versus PNs (78%) (p = 0.009), and fewer TNs (1%) compared to PNs (7%) required ASD intervention (p = 0.02). Most ASDs identified in TNs and PNs spontaneously resolve. PNs, however, demonstrate lower ASD resolution and higher intervention rates within all size groups. These data should inform follow-up of affected neonates.